When I look at penis size and what makes it stand out for me is proportion.
For example an average height man say 5’8-5’10 with an average penis will look.. Well average. But say take the average man’s height, like TNT and strap an 8+inch winky with a 6 inch girth and that thing would look big to me.
Now take that same 8 inch dick with 6 inch girth and put it on a 6’6 250 pound dude and it would look proportionate. It wouldn’t stand out as being huge compared to his body size. But that’s just me.
In terms of length looking better on skinny people ect. I would make the assumption that girth would look better on skinny people because it stands out proportionately. Skinny dude with a fat dick.